|Publication number||US20080173211 A1|
|Application number||US 12/005,995|
|Publication date||Jul 24, 2008|
|Filing date||Dec 28, 2007|
|Priority date||Jan 3, 2007|
|Also published as||CA2616750A1|
|Publication number||005995, 12005995, US 2008/0173211 A1, US 2008/173211 A1, US 20080173211 A1, US 20080173211A1, US 2008173211 A1, US 2008173211A1, US-A1-20080173211, US-A1-2008173211, US2008/0173211A1, US2008/173211A1, US20080173211 A1, US20080173211A1, US2008173211 A1, US2008173211A1|
|Inventors||James S. Kennedy|
|Original Assignee||Kennedy James S|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (9), Classifications (6), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The Constant Contact Side Bearing (CCSB) is a common device for limiting undesirable motion in railroad freight cars. The CCSB typically consists of a contained resilient member (such as, for example, an elastomer mechanical spring, etc.) attached to the truck and maintaining engagement with the freight car body. When the car experiences roll motion due to curving or track irregularities, the CCSB can dissipate a portion of the resulting energy through vertical compression of the resilient member, restoring the system to equilibrium. In addition, the CCSB is capable of controlling hunting by resisting rotation of the truck via frictional sliding between the freight car body wear plate and the CCSB.
Based on these considerations, it is desirable that the CCSB provide consistent and sustainable vertical and longitudinal damping characteristics over a wide range of temperatures and operating conditions for the successful operation of a railcar. Historically, CCSBs with elastomer springs have been the device of choice to meet these rigorous demands of rail service (refer to U.S. Pat. Nos. 3,957,318, 6,092,470 and 6,862,999 herein incorporated by reference). The primary benefits of utilizing elastomer springs includes its excellent damping properties, predictable performance, energy storage per unit volume resulting in smaller footprints, and meeting the design parameter for the vertical and longitudinal stiffness characteristics. However, elastomer springs are subject to compression set and, if not designed properly, they can be susceptible to thermal degradation. As a result, in recent years there has been a growing interest in a CCSB that incorporates metallic compression springs. U.S. Pat. No. 5,806,435 shows special long travel metallic springs. Certainly, steel springs offer potential benefits of lower compression set and improved resistance to thermal degradation. But, they possess insufficient vertical damping (refer to
Therefore, a “hybrid” CCSB consisting of metallic spring or springs in combination with elastomer spring or springs can be used in order to provide more balanced performance by maximizing the advantages and minimizing the disadvantages of both types of springs. For example, metallic steel springs have poor vertical damping, but good resistance to thermal degradation. Whereas, elastomer springs have excellent vertical damping and lower resistance to thermal degradation. By creating a “hybrid” side bearing consisting of metallic and elastomer springs in the proper ratio, one can create a CCSB with a good balance of vertical damping and resistance to thermal degradation. The following table provides an estimate of one such embodiment of a CCSB with metallic, elastomer and hybrid springs.
E = Excellent V = Very Good G = Good F = Fair P = Poor
By this table, it can be seen that by combining metallic and elastomer springs, the hybrid spring CCSB integrates the advantageous properties of each spring type to minimize and/or improve upon the shortcomings, especially in the area of thermal resistance, vertical damping and preload retention, which are essential to the successful performance of a CCSB.
Some of the potential benefits of the hybrid spring are as follows.
The metallic spring can have a higher thermal conductivity than an elastomer and can provide a path for drawing heat away from the wear cap due to friction and thereby reducing the thermal damage to the elastomeric spring.
By sharing the preload between metallic and elastomer springs, each spring can be subjected to lower stresses and thereby reduces the chance of the springs failing.
The impact of any degradation of the elastomer spring can be reduced since the entire load is not being generated by the elastomer or vice versa. For example, if 50% of the preload is generated by the metallic spring and 50% by the elastomer spring, then any preload loss in the elastomer will impact only half of the total preload, resulting in a 50% reduction in potential preload loss.
The elastomer spring will provide the much needed damping properties over the metallic only spring designs. The elastomer spring can be a backup in case of failure in the metallic spring and vice versa. An elastomer spring provides a more gradual decrease in performance over time which is more conducive to a regular maintenance program to maintain acceptable performance.
The CCSB can be less expensive if a mix of metallic and elastomer springs are used as opposed to an all metal spring design.
The very small compression set taken by a metallic spring can help offset the set experienced by an elastomer spring. On the other hand, an elastomer spring intrinsically possesses the ability to provide a minimum amount of creep (a form of stress relaxation). This is advantageous in a constant contact side bearing because it helps the freight vehicle body to settle down on the side bearings to the appropriate setup height and maintain the proper balance of load at the centerbowl/centerplate and an interface. This is especially useful in a newly built freight car or when the freight car is not loaded.
The following is a description of some embodiments of the invention. The hybrid spring constant contact side bearing (CCSB) would typically consist of a housing which attaches to the truck, a wear cap that sits above the housing and contacts the body side bearing wear plate on the underside of the car body, and at least one resilient member that fits inside the housing and below the wear cap and is loaded in compression. In the hybrid spring CCSB, the resilient member would consist of the combination of at least one metallic spring and at least one elastomer member or spring. Designs of this type are shown in
The CCSB can be designed to provide either standard travel or extended (long) travel in terms of vertical deflection of the side bearing. The CCSB can structure to limit vertical travel (deflection) by interaction of existing components, such as the wear cap and housing, or a separate additional component. This solid stop can engage prior to the solid height or travel limit of the metallic and/or elastomer spring.
The resilient member can consist of any of the following or other structures:
Metallic spring and one or more elastomer springs as separate components that nest within each other in the following manner such as, for example, the metallic spring or springs inside the elastomer spring (refer to
One embodiment can use a metallic spring encapsulated within an elastomer material (refer to
The metallic spring(s) and elastomer spring(s) can be placed in series (linked end to end as shown in
The metallic spring(s) could sit on an elastomer base to protect the metallic spring from shock loading. This case could also be a separate component (refer to
There does not necessarily need to be an even number of metallic and elastomer springs. Some applications may use more metallic springs, while other applications use more elastomeric spring units. The resilient member can be loaded in compression, shear, tension or the combination of the three.
The metallic spring can in some embodiments provide anywhere from 5% to 95% of the vertical load with the balance of the vertical load and the vertical damping provided by the elastomer spring. The ratio of the load provided by the metallic spring versus elastomer spring can be determined based on car type, service environment, vertical damping, fatigue life, cost, stress/strain, dimensional considerations and other engineering conditions.
The overall heights of the springs can be as follows:
Each metallic and elastomer spring has the same overall heights.
Each spring, metallic and elastomeric, has its own unique overall height.
Each metallic spring has the same overall height and each elastomer spring has its own elastomer spring height.
The metallic spring is preferably a steel helical spring, torsion spring, volute spring, leaf spring, or any combination thereof.
The elastomer spring can be made of polyurethane elastomer with a hardness ranging from 30 Shore A to 80 Shore D made, such as for example:
MDI polyester cured with HQEE or 1,4 butandiol polyurethane;
MDI polycaprolactone cured with HQEE or 1,4 butandiol polyurethane;
MDI polyether cured with HQEE or 1,4 butandiol polyurethane;
Foam, rubber or other elastomeric material.
The elastomer spring could be made from rubber (natural or synthetic) such as with a hardness ranging from 30 Shore A to 80 Shore D, any material that possesses high damping characteristics (large hysteresis) or any combination of the above materials will usually be desirable.
The metallic and/or elastomer springs may include a structure to assist in positioning these springs relative to the wear cap and/or housing. One such mechanism is to use a hole, through bore or blind, in the springs in combination with a post or boss on the wear cap and/or housing or vice versa. The springs may include a centerhole (refer to
The housing can be fastened to the truck bolster via bolts, rivets, etc., welded directly to the bolster, or inserted into existing bolster pocket which is integral with or has been attached to the truck via fasteners, rivets, welding, etc. The housing can be made of steel, ductile iron, or austempered ductile iron. The housing can be produced from a standard shape such as for example: bar, plate, round channel, by forming, forging, casting and/or fabrication of one or more of these. The housing can have a floor that is integral with the entire housing, open on the bottom allowing the resilient member to contact the bolster, or have a separate base that attaches to the housing to form a floor for the resilient member (refer to Stucki published patent application Ser. No. 10/939,667 for Modular Base Side Bearing). The thickness of the housing floor can be varied to provide different preloads or vertical travel and/or satisfy AAR non-interchangeability requirements. The housing could incorporate an insert or sleeve made of metal (such as brass) or non-metallic material (such as polyurethane) to provide additional vertical and longitudinal stiffness and/or reduce wear. This insert or sleeve can be attached to the housing mechanically, chemically (bonded), or any combination of the two. Also, different floor heights can be used for the metallic and elastomeric spring member.
The wear cap can be made of steel, ductile iron, or austempered ductile iron. The wear cap can be produced from a standard shape (bar, plate, round, channel, etc.) forming, forging, casting, and/or fabrication of one or more of these. The wear cap could include an insert of metal (such as brass) or non-metallic material (such as nylatron, plastic, thermoplastic urethanes or the elastomer spring portion of the hybrid spring) located between the top of the wear cap and underside of the car body or between the wear cap and housing to provide additional resistance to thermal degradation and/or additional resistance to wear. This insert or sleeve can be attached to the housing mechanically, chemically (bonded), or any combination of the two. The wear cap can have different thickness to provide different column heights for the metallic and elastomeric elements.
Although the typical CCSB includes a wear cap and housing as described above, there may be applications where a wear cap and/or housing would be unnecessary in the CCSB.
The embodiments shown in
In the embodiments shown heretofore, the elastomeric spring and the metallic spring can be thought of working in a parallel arrangement. However, a column can be utilized using both the elastomeric spring and the metallic spring in which the two devices are in a series arrangement such that the same force will appear generally in both the metallic and the elastomeric column members.
The ratio of the load provided by the metallic spring versus elastomer spring is generally determined based on one or more of the following: car type, service environment, vertical damping, fatigue life, cost, stress/strain, and dimensional considerations. The spring can be loaded in one or more of the following: compression, shear, tension or a combination such. The metallic spring can provide in the range of 5% to 95% of vertical load; and the balance of the vertical load and the vertical damping primarily provided by the elastomer spring. The metallic springs can be steel and can be a helical spring, torsion spring, leaf spring or combinations of such. The elastomer spring can be a polyurethane elastomer with a hardness generally in the range from 30 Shore A to 80 Shore D. The elastomeric material can include one or more of the following: MDI polyester cured with HQEE or 1,4 butandiol; MDI polycaprolactone cured with HQEE or 1,4 butandiol; or MDI polyether cured with HQEE or 1,4 butandiol, or a foam material. Some embodiments may use an elastomer spring made of a rubber material with a hardness ranging from 30 Shore A to 80 Shore D. The elastomer spring can be bonded to another substrate such as another elastomer, metal, etc. in order to provide the desired force-deflection characteristics. The constant contact side bearing housing can be fastened to the truck bolster via bolts, rivets. or welded directly to the bolster or inserted into existing bolster pocket which is integral with or has been attached to the truck via fasteners, rivets, or welding.
The constant contact side bearing wear cap can include an insert of metal (such as brass) or non-metallic material (such as nylatron or the elastomer spring portion of the hybrid spring) disposed between said wear cap and said car body to provide additional resistance to thermal degradation and/or additional resistance to wear. This insert can be attached to the wear cap by mechanically, chemically, or other structure. The constant contact side bearing can have a housing that incorporates an insert or sleeve made of metal (such as brass) or non-metallic material (such as polyurethane) to provide additional vertical and longitudinal stiffness and/or reduce wear. This insert or sleeve can be attached to the housing by mechanical, or chemical attachment. The constant contact side bearing can include a stop for limiting the vertical travel (deflection) by interaction of existing components such as the housing and wear cap, or by additional mechanical stops. The constant contact side bearing can have the metallic spring is attached to an encapsulated elastomer spring by mechanically or chemically bonding to the metallic spring.
When these embodiments have shown the outer taper on the surface of 104 of an elastomeric spring for a constant contact side bearing, it is to be understood that the inner surface 106 may contain a light taper to provide additional contouring to optimize the spring characteristics of the elastomer as it is compressed. It may be desirable to keep the outer surface at a constant diameter while the inner surface 106 maintains a taper that varies the compression characteristics. In addition, it may be desirable to have cylindrical elastomeric units used within the metallic coil spring so as to center the elastomeric portion of the spring elements and limit the lateral flow of the elastomeric material. Similarly, it may be desirable to maintain a preset distance between the elastomeric material and the metallic spring so as to permit the elastomeric material some radial outward movement before contacting the metallic spring.
While certain embodiments have been shown, it is understood that the concept of using metallic and elastomeric spring elements within a constant contact side bearing may be utilized in other embodiments within the scope of this attached claims.
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7527003 *||May 21, 2008||May 5, 2009||Asf Keystone, Inc.||Railroad freight car sidebearing|
|US7549379 *||Jul 19, 2006||Jun 23, 2009||Amsted Rail Company, Inc||Railway freight car side bearing|
|US7802524 *||Aug 11, 2009||Sep 28, 2010||Wabtec Holding Corp.||Constant contact side bearing assembly with improved cap machining for a railcar|
|US8220766 *||May 21, 2008||Jul 17, 2012||Paul Henry Fuoss||Table guard assembly|
|US8356558 *||Mar 4, 2011||Jan 22, 2013||Ttx Company||Constant contact side bearing|
|US20120051678 *||Sep 1, 2010||Mar 1, 2012||Amsted Rail Company, Inc.||Railroad freight car sidebearing|
|US20120222581 *||Sep 6, 2012||Jon Jeambey||Constant contact side bearing|
|CN102180180A *||Apr 12, 2011||Sep 14, 2011||北京隆轩橡塑有限公司||Elastic side bearing|
|EP2123534A2 *||Jan 27, 2009||Nov 25, 2009||Amsted Rail Company, Inc.||Railroad freight car sidebearing|
|U.S. Classification||105/199.3, 384/423|
|International Classification||B61F5/14, F16C17/04|
|Jan 17, 2008||AS||Assignment|
Owner name: A. STUCKI CO., PENNSYLVANIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KENNEDY, JAMES S.;REEL/FRAME:020378/0974
Effective date: 20080107
|Jul 9, 2010||AS||Assignment|
Owner name: MADISON CAPITAL FUNDING LLC, AS AGENT, ILLINOIS
Free format text: SECURITY AGREEMENT;ASSIGNOR:A. STUCKI COMPANY;REEL/FRAME:024651/0793
Effective date: 20100629